Conventionally known flush toilet apparatuses have included those including what is known as a direct-drive discharge valve apparatus, such as set forth in CN 203049740 U (Patent Document 1), wherein a discharge opening is opened and closed by the up and down movement of a discharge valve body relative to a discharge opening in a reservoir tank portion for storing flush water supplied to a toilet main body portion.
A conventional flush toilet apparatus such as that set forth in Patent Document 1 includes an automatic flush drive unit inside a reservoir tank portion for electrically driving a discharge valve apparatus based on a signal from a sensor or the like detecting the presence of a toilet user; when the automatic flush drive unit is driven, the discharge valve body rises by a predetermined pull-up amount and the discharge opening is opened for a predetermined time. After flush water has been supplied to the toilet main body portion from a reservoir tank portion, the raised state of the discharge valve body is released, and the discharge opening is shut-off by the discharge valve body.
In recent years, on the other hand, with greater design diversity the need has increased for what are known as one-piece flush toilets, in which the reservoir tank portion for storing flush water used for toilet flushing is integrally formed of porcelain.
In such one-piece flush toilets, reservoir tank portions of what is known as the low-silhouette type are frequently adopted, in which the up-down vertical width dimension of the reservoir tank portion is set to be short relative to the left-right horizontal width direction thereof in order to reduce vertical installation space and to assure design characteristics such as external appearance and aesthetics of the toilet, and there is also an increased need to reduce the size of the reservoir tank portion itself.